Virtual Application and Virtual Database servers?

Hi All,

Our client has two enviornments one is 'Test' and the other one is 'Production'. These test and production enviornments do not talk with each other but are using our pplication in a test enviornment, and in production enviornment. Each enviornment has one application server (for our application) and one database server (for database that is bieng used by our application).

My client is going through a server consolidation and virtualization project right now and they are evaluating whether or not these application and database servers are candidates for virtualization. My client need to immediately know if they can virtualize these servers (both Application server and database server) on which we running our application and database respectively. We have other client using application virtual servers but not database server. As a general question what are the pro and cons of using virtual database and virtual application servers? In general where do we recommend it and where we don't and why? Is there any reason why a database server should not be use in Virtual enviornments? My client immediately just trying to get an idea about feasibility.

Thank you all for your prompt help.

Zee